- Some devices don't have SA support.
- Some devices have SA support, but needs to be enabled per-carrier basis.
- VoNR support might be needed for M1 5GNR NSA.
Think of it as VoLTE and VoWiFi support.
LTE deployment was much smoother as it is data-only network, VoLTE deployment is much harder as it is putting voice on top of the existing LTE network. VoWiFi is to compliment VoLTE, relying on the same IMS Core, to enable Voice Calling over WiFi instead of cellular network.
Again, similar issues is happening on 5G.
Most carriers in the world is using 5GNR NSA mode, at least for the foreseeable future. Therefore, many devices that have 5GNR has enabled NSA only.
5GNR SA is currently on early deployment stage, therefore manufacturers ain't interested in rolling out SA support for all carriers, hence using software update to progressively update (if they are willing to do in the first place).
VoNR might also be the hurdle, as 5GNR SA devices would have to fall back to LTE or 5GNR NSA if they want voice call and the device/network doesn't support.
This is why first gen devices is problematic, and paying for the new technology tax might not always make the most sense.
Unless your aim is to flex about the new technology, you are better off waiting until it's matured.